Steel Shipping Containers 101: Materials and Terminology

Shipping containers come in two major sizes – 20’ and 40’ – and a wide variety of colors. But beyond these slight differences, steel shipping containers are largely manufactured with the same materials and components as one another. Let’s break down the key shipping container materials and terminology you need to know if you are purchasing, building, or modifying a shipping container for your own purposes. 

Recommended Reading: Buyer’s Guide To Shipping Containers


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Steel Shipping Container Components

Since shipping containers need to be made to specific standards that ensure container longevity as well as user and product safety, most of them have the same number and types of components. 

Let’s break those down now.

Component #1) Vents

Most shipping containers feature vents which allow air flow in and out of the container and help with temperature regulation and moisture control. Vents can be made with the same type of Corten steel as the containers or from other metals. Some aftermarket vents can also be durable plastic.

Component #2) Corner Castings and Posts

Corner castings are reinforced shipping container corners that often have openings for twist locks. These corner castings and posts are designed to be strong enough to be rigged to cranes, even if they have a full shipment of goods inside.

Component #3) Beams/Joists/Cross Members

Cross members, which may also be called beams and joists, support shipping container floors by “crossing” from side to side. These cross members can lift the greater shipping container structure off the ground, which is also why many shipping container structures don’t need foundations. Cross members create extra space between the ground and the flooring to stop moisture from actually affecting the floor of the shipping container proper.

Component #4) Cargo Doors, Headers, and Sills

Most shipping containers will have maneuverable cargo doors split down the middle to form two separate steel doors. These are usually quite sturdy and secure and may contain one or more different locking or securing mechanisms.

All shipping containers will also make use of a number of headers and sills. Headers are frames at the top of the shipping container while threshold sills border the other sides of a shipping container’s opening.

Component #5) Forklift Slots/Pockets

Any shipping containers designed to be moved from place to place will contain two forklift pockets or slots along the bottom edge of their shapes. These are in place to allow forklifts to pick up shipping containers and move them around – forklift tines are simply inserted into the pockets when ready. Note that not all used containers will have forklift pockets.

Component #6) Flooring

The vast majority of shipping containers will come with durable flooring made of one or more materials. Floorings are usually infused with insecticides and other protective coatings to ensure that they last for a long time and don’t suffer from insect or rodent damage. 

Component #7) Security Seals

Many shipping containers may have their security bolstered by security seals. These are often color-coded and numbered and can be combined with standard locking mechanisms to seal a shipping container until it reaches its destination.

Security seals are useful since it’s easy to tell if a shipping container has been opened ahead of time; if the seal is broken, you have a problem.

Component #8) Twist Locks

Any shipping containers designed to be connected to others will feature twist locks. These can securely latch shipping containers either to counterpart containers or to other anchor points depending on your needs. These locks work by fitting into corner castings, then pivoting to a locked position through the use of a lever or another manual control.

Recommended Reading: How to Join Shipping Containers Together

Component #9) CSC Plate

A CSC (which stands for The International Convention for Safe Containers) plate indicates that a shipping container meets certain design and construction standards. Such plates essentially mark a shipping container as safe to use. These plates are usually affixed to the interior or exterior of a container.

What Type of Steel Are Shipping Containers Made Of?

Shipping containers and the majority of their components are made of metal. But not just any metal is used for their crucial parts, walls and doors. Instead, most shipping containers are constructed from high-quality Corten steel.

Corten Steel

Also called “weathering steel”, Corten steel is forged by combining several steel alloys and doesn’t need to be painted to resist corrosive damage. This makes Corten steel a particularly good material for shipping containers and their surfaces, which are often exposed to corrosive elements or materials like saltwater.

Corten steel is also valuable because it’s extremely easy material to use for welding and shaping. While it’s still good to paint shipping containers if possible, the nature of Corten steel means that any rust that does form shouldn’t penetrate lower than the initial layer of paint.

Shipping container walls, frames, corner castings, and other major metal components will almost universally be made from Corten steel.

Other Shipping Container Materials

Certain components in a shipping container may also be made with additional materials. For instance, shipping container floors are often made with either bamboo or marine-grade plywood.

Bamboo Flooring

Bamboo flooring is the less common of the two options. However, you can still find it in many older shipping containers since bamboo is extremely durable and is resistant to mildew. Furthermore, many shipping container structures and restaurants appreciate bamboo flooring for its aesthetics. It’s easy to tell whether a shipping container’s floor is made of bamboo or another type of wood since bamboo floors have woven patterns.

Marine-Grade Plywood

Most modern shipping containers use marine-grade plywood, which has recently become much cheaper and more available for manufacturers. Most marine-grade panels are infused with insecticides to stop insects from chewing through the material over the course of a long voyage.

Such plywood is also water-resistant to a limited degree, although some floorings will include additional water-resistant coatings to boost this effect. Marine-grade plywood is durable, flexible, and easy to install in new shipping containers, making it a prime choice for folks constructing their own containers for shipping or other purposes.

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